The tuning system for a high frequency receiver, particularly an AM receiver for vehicles, comprises a tunable input resonance circuit having a variable inductance formed by the signal winding of a controllable inductor. The control winding of the inductor is supplied with a control current. The control...http://www.google.com/patents/US4450588?utm_source=gb-gplus-sharePatent US4450588 - Tuning system for a high frequency receiver utilizing a controllable inductor
